68 lines
1.5 KiB
JavaScript
68 lines
1.5 KiB
JavaScript
var Buffer = require('safe-buffer').Buffer
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function decode (buffer, maxLength, minimal) {
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maxLength = maxLength || 4
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minimal = minimal === undefined ? true : minimal
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var length = buffer.length
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if (length === 0) return 0
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if (length > maxLength) throw new TypeError('Script number overflow')
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if (minimal) {
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if ((buffer[length - 1] & 0x7f) === 0) {
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if (length <= 1 || (buffer[length - 2] & 0x80) === 0) throw new Error('Non-minimally encoded script number')
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}
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}
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// 40-bit
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if (length === 5) {
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var a = buffer.readUInt32LE(0)
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var b = buffer.readUInt8(4)
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if (b & 0x80) return -(((b & ~0x80) * 0x100000000) + a)
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return (b * 0x100000000) + a
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}
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var result = 0
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// 32-bit / 24-bit / 16-bit / 8-bit
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for (var i = 0; i < length; ++i) {
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result |= buffer[i] << (8 * i)
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}
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if (buffer[length - 1] & 0x80) return -(result & ~(0x80 << (8 * (length - 1))))
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return result
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}
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function scriptNumSize (i) {
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return i > 0x7fffffff ? 5
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: i > 0x7fffff ? 4
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: i > 0x7fff ? 3
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: i > 0x7f ? 2
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: i > 0x00 ? 1
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: 0
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}
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function encode (number) {
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var value = Math.abs(number)
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var size = scriptNumSize(value)
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var buffer = Buffer.allocUnsafe(size)
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var negative = number < 0
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for (var i = 0; i < size; ++i) {
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buffer.writeUInt8(value & 0xff, i)
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value >>= 8
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}
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if (buffer[size - 1] & 0x80) {
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buffer.writeUInt8(negative ? 0x80 : 0x00, size - 1)
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} else if (negative) {
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buffer[size - 1] |= 0x80
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}
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return buffer
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}
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module.exports = {
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decode: decode,
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encode: encode
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}
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